Perfluoroalkylation process

ABSTRACT

Perfluoroalkylaromatic compounds containing at least two carbons in the perfluoroalkyl group are prepared by reacting an aromatic bromide or iodide with a potassium perfluoroalkanoate corresponding to the formula KOOC(CF 2 ) n  CF 3  wherein n is an integer of at least one in the presence of cuprous iodide and a dipolar aprotic solvent.

FIELD OF INVENTION

This invention relates to perfluoroalkylaromatic compounds and moreparticularly to a process for preparing them.

BACKGROUND

As disclosed in McLoughlin et al., Tetrahedron, Vol. 25, pp. 5921-5940,1969, Kobayashi et al., Tetrahedron Letters, No. 42, pp. 4071-4072,1979, Gassman et al., Tetrahedron Letters, Vol. 26, No. 43, pp.5243-5246, 1985, and U.S. Pat. Nos. 3,408,411 (McLoughlin et al.) and4,439,617 (Sestanj et al.), it is known that perfluoroalkylaromaticcompounds are apt to be useful as biologically-active compounds,surfactants, coatings, sealants, dyestuffs, alkyd-type resins, etc.; andthey can be prepared in various ways. Matsui et al., Chemistry Letters,1981, pp. 1719-1720, teach that aromatic halides may betrifluoromethylated with sodium trifluoroacetate in the presence ofcuprous iodide and a dipolar aprotic solvent. Copending application Ser.No. 724,474 (Ramachandran et al.), filed Apr. 18, 1985, now U.S. Pat.No. 4,590,010, discloses the use of the technique of Matsui et al. intrifluoromethylating 6-alkoxy-5-halo-1-cyanonaphthalenes and hydrocarbyl6-alkoxy-5-halo-1-naphthoates.

SUMMARY OF INVENTION

An object of this invention is to provide a novel process for preparingperfluoroalkylaromatic compounds containing at least two carbons in theperfluoroalkyl group.

This and other objects are attained by (A) reacting an aromatic bromideor iodide with at least about one equivalent of a potassiumperfluoroalkanoate corresponding to the formula:

    KOOC(CF.sub.2).sub.n CF.sub.3

wherein n is an integer of at least one in the presence of cuprousiodide and a dipolar aprotic solvent and (B) if desired, subjecting theproduct to one or more additional reactions to form a derivative.

DETAILED DESCRIPTION

Aromatic halides utilizable in the practice of the invention aresubstituted and unsubstituted aromatic iodides and bromides wherein anysubstituents are inert substituents (i.e., substituents that do notprevent the reaction from occurring) such as alkyl, alkoxy, alkylthio,aryl, aryloxy, arylthio, cyano, nitro, acylamino, alkylamino, tertiaryamino, sulfonamido, sulfone, sulfonyl, phosphino, perfluoroalkyl,chloro, fluoro, ester, aldehyde, ketone, acetal, sulfono groups, etc.,and the aromatic ring may be a carbocyclic ring such as a benzene,naphthalene, anthracene, etc., ring or a five- or six-memberedheterocyclic ring having aromatic character, e.g., a pyridine,quinoline, isoquinoline, thiophene, pyrrole, furan, etc., ring.Exemplary of such compounds are iodobenzene, 3-iodotoluene,4-chloroiodobenzene, 4-iodomethoxybenzene, 1-iodonaphthalene,3-iodoaniline, 1-iodo-3-nitrobenzene, 2-iodothiophene,4-iodoisoquinoline, 2-iodopyridine, 3-iodoquinoline, the correspondingbromides, etc.

In a preferred embodiment of the invention, the aromatic halide is ahalonaphthalene corresponding to the formula: ##STR1## wherein R and R'are independently selected from chloro, fluoro, nitro, hydroxy, andalkyl and alkoxy substituents containing 1-6 carbons; Q is --CN or--COOR"; R" is saturated hydrocarbyl; X is bromo or iodo; and m is 0 or1.

The halocyanonaphthalenes and halonaphthoates utilizable in the practiceof the invention may be any compounds corresponding to the abovehalonaphthalene formula, but they are preferably compounds wherein m is0, X is in the 5-position, and R is an alkyl or alkoxy substituent inthe 6-position. When the R and R' substituents are alkyl or alkoxy, theyare generally straight-chain groups of 1-3 carbons or branched-chaingroups of three or four carbons, such as methyl, ethyl, propyl,1-methylethyl, butyl, 2-methylpropyl, 1,1-dimethylethyl, thecorresponding alkoxy groups, etc., although, as indicated above, largergroups such as hexyl and hexanoxy are also utilizable. When thehalonaphthalene is an ester, R" may be any saturated hydrocarbyl group(i.e., a hydrocarbyl group that is free of aliphatic unsaturation) butis preferably an alkyl, cycloalkyl, aryl, alkaryl, or aralkyl groupcontaining 1-10 carbons, e.g., methyl, ethyl, propyl, cyclohexyl,phenyl, tolyl, benzyl, etc. Particularly preferred halonaphthalenes are6-alkoxy-5-bromo-1-cyanonaphthalenes,6-alkoxy-5-iodo-1-cyanonaphthalenes, 6-alkoxy-5-bromo-1-naphthoates, and6-alkoxy-5-iodo-1-naphthoates, especially those compounds wherein thealkoxy groups are methoxy.

The halonaphthoates are known compounds. The halocyanonaphthalenes arecompounds that can be prepared by cyanating the appropriatelysubstituted tetralone, e.g., 6-methoxytetralone, to form theappropriately substituted 1-cyano-3,4-dihydronaphthalene, e.g.,6-methoxy-1-cyano-3,4-dihydronaphthalene, aromatizing the product in anysuitable manner, and brominating or iodinating the resultant substituted1-cyanonaphthalene by known techniques.

As already mentioned, the halonaphthalene or other aromatic halide isreacted with at least about one equivalent of a potassiumperfluoroalkanoate to form the corresponding perfluoroalkylaromaticcompound. Since there does not appear to be any maximum to the number ofCF₂ groups that can desirably be incorporated into the aromaticmolecule, the potassium perfluoroalkanoate employed in the reaction maybe any compound corresponding to the formula KOOC(CF₂)_(n) CF₃ wherein nis an integer of at least one, and it is generally the salt whichcontains the same number of CF₂ groups as is desired in the product.However, because of cost and availability factors, as well as the factthat the reaction typically permits the formation of at least someperfluoroalkylaromatic compound containing more CF₂ groups in thesubstituent than are present in the perfluoroalkanoate, the preferredreactants are those containing about 1-6 CF₂ groups, such as potassiumpentafluoropropionate, heptafluorobutyrate, nonafluorovalerate,tridecafluoroheptanoate, pentadecafluorooctanoate,heptadecafluorononanoate, nondecafluorodecanoate, etc. There does notappear to be any maximum to the amount of salt that may be employed.However, as a practical matter, the amount used is generally in therange of about 1-20 equivalents, preferably at least about 1.5equivalents.

Dipolar aprotic solvents that may be utilized include, e.g.,N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide,hexamethylphosphoric triamide, dimethylsulfoxide, etc., but theparticular solvent employed does not appear to be critical except in thesense that it should have an appropriate boiling point for use at thereaction temperatures to be utilized. The solvent is used in solventamounts, e.g., an amount such as to provide an organic solidsconcentration of up to about 15%.

The cuprous iodide may be employed in any suitable amount, generally anamount in the range of about 0.5-5 equivalents.

The reaction is conducted by combining the ingredients in any convenientorder and heating them at a suitable temperature, conveniently refluxtemperature, to accomplish the desired perfluoroalkylation. Anhydrousconditions are preferably employed, and the temperature is generally inthe range of about 130°-160° C., preferably about 140°-155° C.

The perfluoroalkylnaphthalene products of the preferred reaction, liketheir trifluoromethyl homologs, can be subjected to reactions such asthose taught by Sestanj et al., the teachings of which are incorporatedherein in toto by reference. Thus, e.g., (1) a(perfluoroalkyl)cyanonaphthalene or perfluoroalkylnaphthoate prepared bythe perfluoroalkylation reaction may be hydrolyzed to the correspondingacid in the presence of a base such as sodium or potassium hydroxide,(2) the acid can be halogenated, e.g., by reaction with thionylchloride, to form the corresponding acid halide, (2) the acid halide maybe reacted with a saturated hydrocarbyl ester of an acid correspondingto the formula ZNHCH₂ COOH (e.g., methyl, ethyl, propyl, cyclohexyl,phenyl, tolyl, or benzyl sarcosinate, the corresponding esters ofaminoacetic acids having other N-substituents containing 1-6 carbons,such as N-ethyl, N-propyl, etc.) to form an amide corresponding to theformula: ##STR2## (3) the amide may be saponified to form thecorresponding salt, then hydrolyzed to the corresponding acid, and thenthiated, e.g., with phosphorus pentasulfide or the like, to form athioamide corresponding to the formula: ##STR3## or (4) the thioamidemay be prepared by thiating the amide and then subjecting the product tothe saponification and hydrolysis steps.

The invention is advantageous in that it provides a means of preparingperfluoroalkyl compounds useful in various applications, such assurfactants, coatings, sealants, resins, dyestuffs, etc., as well asbiologically-active materials or precursors therefor.

The following examples are given to illustrate the invention and are notintended as a limitation thereof.

EXAMPLE I

A suitable reaction vessel was charged with 8.1 g of6-methoxy-5-bromo-1-cyanonaphthalene, 11.8 g of CuI, 35 ml of toluene,and 55 ml of N,N-dimethylformamide. The reaction mixture was heated to165° C. with concurrent azeotropic removal of toluene/water (25 ml) andthen maintained at 155° C. when 11.8 g of potassiumpentafluoropropionate was added. The reaction was monitored by VPC.After five hours no starting material was detected and the reactionmixture was poured into 150 ml of water and 125 ml of methylenechloride. The two phases were filtered, after which the organic layerwas separated, washed with brine, and concentrated in vacuo to provide acrude 6-methoxy-5-pentafluoroethyl-1-cyanonaphthalene (6-MPCN) having apurity of greater than 95%.

EXAMPLE II

The crude 6-MPCN product of Example I was dissolved in 135 ml ofmethanol and 40 ml of a potassium hydroxide solution (4.5 g of KOH in 40ml of water) and heated to 125° C./70 psi for seven hours. The reactionmixture was then worked up and acidified to yield 6.6 g of6-methoxy-5-pentafluoroethyl-1-naphthoic acid.

It is obvious that many variations may be made in the products andprocesses set forth above without departing from the spirit and scope ofthis invention.

What is claimed is:
 1. A process which comprises reacting an aromaticbromide or iodide with at least one equivalent of a potassiumperfluoroalkanoate corresponding to the formula KOOC(CF₂)_(n) CF₃wherein n is an integer of at least one in the presence of cuprousiodide and a dipolar aprotic solvent.
 2. A process which comprisesreacting a halonaphthalene corresponding to the formula: ##STR4## withat least about one equivalent of a potassium perfluoroalkanoatecorresponding to the formula KOOC(CF₂)_(n) CF₃ wherein n is an integerof at least one in the presence of cuprous iodide and a dipolar aproticsolvent so as to form a perfluoroalkylnaphthalene corresponding to theformula: ##STR5## in which substituted naphthalene formulas R and R" areindependently selected from chloro, fluoro, nitro, hydroxy, and alkyland alkoxy substituents containing 1-6 carbons; Q is --CN or --COOR"; R"is saturated hydrocarbyl; X is bromo or iodo; m is 0 or 1; and n is aninteger of at least one.
 3. The process of claim 2 wherein Q is --CN. 4.The process of claim 2 wherein m is 0, X is in the 5-position, and R isan alkyl or alkoxy substituent in the 6-position.
 5. The process ofclaim 2 wherein the halonaphthalene is6-methoxy-5-bromo-1-cyanonaphthalene.
 6. The process of claim 2 whereinthe halonaphthalene is 6-methoxy-5-iodo-1-cyanonaphthalene.
 7. Theprocess of claim 2 wherein the amount of potassium perfluoroalkanoateused is about 1-20 equivalents.
 8. The process of claim 2 wherein a6-alkoxy-5-bromo-1-cyanonaphthalene is reacted with about 1-20equivalents of potassium perfluoroalkanoate.
 9. The process of claim 8wherein the alkoxy group is methoxy.
 10. The process of claim 2 whereina 6-alkoxy-5-iodo-1-cyanonaphthalene is reacted with about 1-20equivalents of potassium perfluoroalkanoate.
 11. The process of claim 10wherein the alkoxy group is methoxy.
 12. The process of claim 2 whereinthe amount of cuprous iodide used is about 0.5-5 equivalents.
 13. Theprocess of claim 2 wherein the reaction temperature is about 130°-160°C.
 14. The process of claim 13 wherein the reaction temperature is about140°-155° C.